March 22, 2010

Sesame Street Revisited: Interviewing Vegetable Puppets about CO2

Filed under: Agriculture

Back in November, Sesame Street celebrated its 40 anniversary, and the show featured First Lady Michelle Obama talking to vegetable puppets about helping curb childhood obesity. The First Lady explained to three young children and two somewhat old muppets the logistics of planting and growing tomatoes, lettuce and carrots as part of her initiative to promote healthy eating. She mentioned that eating these vegetables can make the children big and strong. At the end of the show, the cabbage puppet told her “We think you’re great too” and then led the children in three cheers for the First Lady. Mrs. Obama said at the time of recording her appearance was “probably the best thing I’ve done so far in the White House.”

We at World Climate Report were so moved by this show that we decided to ask the vegetable puppets what would make them big and strong, and the answer we got in our exclusive interview was resoundingly … “higher levels of atmospheric carbon dioxide (CO2)!”

There are 1,000s of articles in the professional literature showing the incredible biological benefits of CO2, so in honor of the Sesame Street’s 40th Anniversary, here is the latest on tomatoes, cabbage, lettuce and carrots.

Let’s start with tomatoes. A recent article in Pedosphere was produced by eight scientists from China and New Zealand. They grew tomato plants hydroponically in near ambient CO2 concentrations (near 350 ppm) and in elevated concentrations (near 800 ppm). Wang et al. reported in their abstract “Compared with the control, CO2 enrichment significantly increased the dry matter of both shoot and root, the ratio of root to shoot, total root length, root surface area, root diameter, root volume, and root tip numbers, which are important for forming a strong root system. The elevated CO2 treatment also significantly improved root hair development and elongation, thus enhancing nutrient uptake.” Obviously, elevated CO2 definitely makes tomato plants bigger and stronger, and we hope the First Lady is thrilled at these results.

With the tomatoes doing fine, let’s turn our attention to carrots. A team of five scientists from Canada’s Nova Scotia Agricultural College and Mississippi State University grew four types of carrots in a controlled environment room with carrots grown at various levels of atmospheric CO2; results were published in Photosynthetica. When comparing the near-ambient (350 ppm) and elevated (650 ppm) CO2 levels, all four carrot types increased the rate of photosynthesis, PN, by 43%, decreased stomatal conductance, gs, by 17% thereby reducing evaporation rate, E, by 15%, and increasing the water use efficiency of the plants by an amazing 75%! Kyei-Boahen et al. concluded their article stating in the final sentence “These results suggest that future enrichment in the atmospheric CO2 may lead to adjustments in PN and gs, which could improve carrot productivity and water utilization.”

As we now turn to cabbage, we will expose another remarkable benefit of elevated atmospheric CO2 concentrations. Like virtually every other plant on the Earth, elevated CO2 will cause cabbage to grow faster and bigger while using less water. Cabbage is particularly vulnerable to a chewing insect, called the diamondback moth, that can spoil all the fun. Recognizing the serious threat of this insect, a team of four scientists from Finland grew several types of cabbage in ambient (360 ppm) and double ambient (720 ppm) atmospheric CO2 concentrations. However, the focus of the Reddy et al. group was not on the cabbage, but on the larvae feeding on the plants. Plants produce a remarkable array of chemicals to protect themselves from the unwanted herbivores, and you guessed it … cabbage in elevated CO2 severely stunted the growth of the larvae. One of the cabbage varieties decreased the relative growth rate of the larvae by 45% while the other decreased the rate by 65% given elevated CO2. In their abstract, the authors note that this negative impact on the larvae is “quite strong”—just the kind of words Mrs. Obama spoke about on Sesame Street.

And now for some good news about lettuce. Six scientists from China and Australia tell us in their introduction that “It is considered that the optimal concentration of carbon dioxide (CO2) for plant growth is 800–1000” ppm. We agree wholeheartedly and wonder why so many people refuse to acknowledge the incredible biological benefit plants receive from elevated CO2. Jin et al. introduced a method of increasing CO2 concentrations in greenhouses by composting plant residues and animal manures (you might wait to try this in your own home). They tested their idea and found they could double atmospheric CO2 in the greenhouses with the composting materials. They grew plants in these greenhouses, and the edible shoot weight of leaf lettuce increased by 257% while for stem lettuce, the yield increased by 87%. If you are interested, celery yield increased by 270% and Chinese cabbage increased yield by 227% — all thanks to elevated CO2.

So when we talked to the vegetable puppets on Sesame Street, they gave three cheers all right—a three cheers for higher levels of atmospheric CO2!

References:

Jin, C., S. Du, Y. Wang, J. Condon, X. Lin, and Y. Zhang. 2009. Carbon dioxide enrichment by composting in greenhouses and its effect on vegetable production. Journal of Plant Nutrition and Soil Science, 172, 418-424.

Kyei-Boahen, S., T. Astatkie, R. Lada, R. Gordon, and C. Caldwell. 2003. Gas exchange of carrot leaves in response to elevated CO2 concentration. Photosynthetica, 41, 597-603.

Reddy, G.V.P., P. Tossavainen, A.-M. Nerg, and J.K. Holopainen. 2004. Elevated atmospheric CO2 affects the chemical quality of Brassica plants and the growth rate of the specialist, Plutella xylostella, but not the generalist, Spodoptera littoralis. Journal of Agricultural and Food Chemistry, 52, 4185-4191.

Wang, Y., S.-T, Du, L.-L. Li, L.-D. Huang, P. Fang, X.-Y. Lin, Y.-S. Zhang, and H.L. Wang. 2009. Effect of CO2 elevation on root growth and its relationship with indole acetic acid and ethylene in tomato seedlings. Pedosphere, 19, 570-576.




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